Device for selective combustion in a multicylinder engine

ABSTRACT

A device for saving fuel and cleansing exhaust gas in a multicylinder automobile engine, by interrupting fuel supply to selected cylinders of the engine during deceleration and coasting of the automobile. The device comprises valves mounted in the selected cylinders of the engine, a pressure-sensing means to sense the negative pressure at the intake manifold of the engine, and a connecting means to operatively connect said pressuresensing means to said valves. The valves are closed by the pressure-sensing means when the negative pressure at the engine intake manifold exceeds a certain predetermined level due to deceleration or slow running of the automobile.

United States Patent [72] lnventors Yasuo Nakajima;

Yoshimasa Ilayashi, Yokohama, Japan [21 Appl. No. 775,239 [22] Filed Nov. 13, 1968 [45] Patented May 11, 1971 [73] Assignee Nissan .Iidsha Kabrishiki Kaisha Yokohama, Japan [32] Priority Jan. 25, 1968 [3 3] Japan [31 43/3986 [54] DEVICE FOR SELECTIVE COMBUSTION IN A MULTICYLINDER ENGINE 7 Claims, 5 Drawing Figs.

[52] US. Cl. 192/.062, 123/97(B), 123/198(F) [51] Int. Cl. ..I l6d 21/04, F02d 9/00 [50] FieldofSearch 123/198 (F), 97 (B); l92/.062

[56] References Cited UNITED STATES PATENTS 1,410,098 3/ 1922 Hamilton 123/ 198 Primary Examinerwendell E. Burns Attorney-Sughrue, Rothwell, Mion, Zinn & MacPeak ABSTRACT: A device for saving fuel and cleansing exhaust gas in a multicylinder automobile engine, by interrupting fuel supply to selected cylinders of the engine during deceleration and coasting of the automobile. The device comprises valves mounted in the selected cylinders of the engine, a pressuresensing m'eans to sense the negative pressure at the intake manifold of the engine, and a connecting means to operatively connect said pressure-sensing means to said valves. The valves are closed by the pressure-sensing means when the negative pressure at the engine intake manifold exceeds a certain predetermined level due to deceleration or slow running of the automobile.

PAIENTEMAYHISW 3,578,116

a winner 4 OFF DEVICE FOR SELECTIVE COMBUSTION IN A MULTICYLINDER ENGINE The present invention relates to an apparatus for saving fuel and cleansing the exhaust gas in a multicylinder vehicle engine having at least one intake manifold with a carburetor means and a plurality of branches communicating engine cylinderinlets with the manifold.

Generally speaking, when a vehicle having a gasoline engine is coasting, the mixture of fuel and air fed to the engine does not burn completely in the combustion chamber, resulting in a discharge of a large amount of hydrocarbons from the engine exhaust to the atmosphere, and the increase in the hydrocarbon discharge causes air contamination.

The reason for incomplete combustion of the supply gas mixture in the combustion chamber during coasting is due to the fact that the intake amount of air in the supply gas mixture decreases and a large amount of residual gas stays in the combustion chamber during the coasting, so that either ignition fails or the barely ignited combustion dies out without spreading through the combustion chamber; This is one of the problems related to the fundamental structure of 'intemal combustion engines, and the only way to effectively burn the supply gas mixture in the combustion chamber under such conditions is to increase the intake amount of the supply gas mixture to the combustion chamber.

A known method of preventing air contamination is to retard the spark advance during idling, and to keep the enginerevolving speed at a comparatively high level, so as to improve the fuel combustion in the combustion chamber as far as possible. With a high revolving speed, the idling throttle valve opening is increased to allow a large intake amount of the supply gas mixture during the deceleration. However, such niethod has a disadvantage in that the throttle valve cannot be opened widely due to the danger of overheating and the occurrence of run-on phenomenon.

An object of the present invention is to obviate the aforesaid difficulties of the known air contamination preventing devices, by providing an improved device for effectively preventing the air contamination and at the same time reducing the fuel consumption. The operative principles of the device according to the present invention are as follows.

When the degree of throttle valve opening of an automobile engine is kept constant during idling, then the intake amount of the supply gas mixture during coasting of the automobile becomes constant. Under such conditions, if the intake of the supply gas mixture to one half of the cylinders of the automobile engine is interrupted by providing suitable valves in those cylinders, while the supply gas mixture is burnt in the remaining half of the cylinders, then, such remaining cylinders receive an amount of the supply gas mixture twice as much in volume as in the case of feeding the mixture to all the cylinders, so that the combustion in the remaining half of the cylinders is improved. For instance, with an engine adapted to burn the supply gas mixture at a speed up to 1,500 r.p.m. during deceleration, that is in coasting condition, it is possible to burn the supply gas mixture in the engine at a speed up to 3,000 r.p.m. by limiting the fuel supply to only one half of the cylinders.

Another object of the present invention is to fulfill the function of preventing air contamination without sacrificing the effectiveness of the engine-braking action, as experienced in the case of known device controlling the negative pressure at the intake manifold, and without causing any mechanical shocks as experienced with a known device limiting fuel shut off.

For a better understanding of the invention, reference is made to the accompanying drawings, in which:

FIG. 1 is a partial sectional plan view of the inlet pipe of a four-cylinder-type engine with a device according to the present invention, shown with a carburetor removed therefrom;

FIG. 2 is a schematic composite vertical sectional view, prepared by combining a section at the line [HI and another section at the line II-Il of FIG. 1;

usable in the embodiment of FIG. 4.

Same parts and members are designated by same numerals and symbols throughout the drawings.

Referring to FIGS. I and 2, a carburetor 1, having venturies 2 and throttle valves 3, is connected to an intake manifold 4 with branches 5, 6, 7, and 8. FIG. 1 illustrates .an engine with four cylinders, but the number of cylinders is not limited to four, but any other number of plural cylinders can be used. The dash-dot lines 9 of FIG. 2 represent a cylinder head.

In the device according to the present invention, butterfly valves 10 are mounted on branches 6 and 7, in such a manner that the butterfly valves are rotatable around the shafts 11 secured to the intake manifold across the branches. An arm 12 is secured to the shaft 11. In the particular embodiment of the device of the present invention, as depicted in FIGS. I and 2, one end of a pipe 13 is connected to open in the wall of the intake manifold 4 at a position of upstream of the butterfly valves 10, and the opposite end of the pipe I3 is communicated with a cylinder 15 having a piston 14 slidably fitted therein. The piston 14 has a hollow chamber 14a formed inside thereof and communicated with the pipe 13, throughholes 14b communicating the hollow chamber to the outside of the piston 14, and an annular recess 14c formed on the outer periphery of the piston 14. The cylinder 15 has an annularrecess formed on the inner peripheral surface thereof. A port 16 is bored at the bottom of the annular recess 150 so as to communicate the inside of the cylinder 15 with another cylinder 20 to be described later. The cylinder 15 has an additional opening 17 bored in the proximity of the annular recess 150, a stop ring 18 fitted on the inner surface of the cylinder 15 at the right-hand end thereof for stopping the piston 14, and a spring 19 fitted between the left-hand end of the cylinder 15 and the left-hand end of the piston I4, as shown in FIG. 2.

The cylinder 20 is connected to the aforesaid cylinder IS in such a manner that the port 16 communicates with the two cylinders 15 and 20. A piston 21 slidably fitted in said other cylinder 20 has a piston rod 22, which is connected to the free end of said arm through a link 23. A spring 24 is engaged with the arm 12 to force the arm 12 to a counterclockwise direction and the link 23 downwards, as seen in FIG. 2.

The branches 6, 7 have holes 25 bored thereon at positions between the respective butterfly valves 10 and the cylinder I head 9. The holes 25 of the branches 6 and 7 are communicated with each other through a tube 26. A short open tube 27 is connected to the tube 26 so as to communicatethe inside of the tube 16 with the atmosphere. A valve lever 28 is pivotally supported by the branch passage portion 7 by means of a pin 29, to selectively close and open the upper end opening-of the open tube 27. A projection 30 is secured to the piston rod 22 in such a manner that when the butterfly valve 10 is closed, the projection 30 raises the free end of the valve lever 28 to open the upper end opening of the tube 27. A packing 31 is mounted on that portion of the valve lever 28 where the hole 27 engages the valve lever 28, and a spring 32 engages the valve lever 28 so as to bias the valve lever 28 toward the lowered position, as seen in FIG. 2, for keeping the open tube 27 closed. I

The operation of the device of thepresent invention, having the aforesaid construction, will now be described. The solid lines in FIGS. 1 and 2 illustrate-the device under the conditions when the automobile is neither decelerating nor coasting.

In other words, when the automobile is in conditions other than deceleration and coasting, the negative pressure at the engine intake manifold, which acts on the piston 14 through the pipe I3, is so low-that the elasticity of the spring 19 surpasses the negative pressure, and hence, the piston 14 assumes the position as illustrated in FIG. 2. Thus, the space A in the cylinder 20 'above the piston 21 communicates with the atmosphere through the port 16 and the hole 17. Accordingly, the link 23 is kept at the lower position by the spring 24 and the butterfly valve remains open.

Then, let it be assumed that the throttle valves 3 of the carburetor 1 are closed. The negative pressure at the intake manifold now increases and forces the piston 14 leftwards against the elasticity of the spring 19, as seen in FIG. 2. When the piston 14 has moved to the left-hand position, the communication between the opening 17 and the port 16 of the cylinder is interrupted by closing the opening 17 with the nonrecessed surface of the piston 14, and at the same time, the through-holes 14b of the piston 14 becomes to face the annular recess 15a formed on the inner surface of the cylinder 15, and hence, the hollow chamber 14a of the piston 14 communicates with the space A above the piston 21 through the holes 14b, the annular recess 15a, and the port 16. Accordingly, the thus increased negative pressure at the intake manifold is delivered to the space A, so as to pull up the piston 21. As a result of it, the arm 12 rotates clockwise, as shown by the arrow B in FIG. 2, through the piston rod 22 and the link 23, so as to close the butterfly valves 10, as shown by dash-dot lines. Thus, the supply gas mixture is absorbed only by the cylinder branches 5 and 8 having no butterfly valves 10, so that the amount of the supply gas mixture to the branches 5 and 8 is considerably increased and the combustion conditions in the engine is greatly improved.

In the embodiment, as shown in FIGS. 1 and 2, the downstream side space of the butterfly valves 10 is communicatable with the atmosphere through the holes 25, the tube 26, and the short open tube 26 blockable by the valve lever 28. The projection 30 secured to the piston rod 22 connected to the piston 21 engages the free end of the valve lever 28 upon the closure of the butterfly valve 10, so that the valve lever 28 turns clockwise against the elasticity of the spring 32, as seen in FIG. 2, to deblock the short tube 27. As a result of it, the atmospheric pressure enters into the back of the butterfly valves 10 through the short tube 27, the tube 26, and the holes 25. Thus, the pressure at the back of the butterfly valves 10 increases to insure the complete interruption of the supply gas mixture by stopping the leakage through fine gaps around outer periphery of the butterfly valves 10. Furthermore, the air delivered to the back of the butterfly valves 10 through the holes 25 proceeds to the exhaust tube and acts to oxidize the incompletely burnt hydrocarbons contained in the exhaust gas to convert them into hannless carbon dioxide gas. Thereby, the cleansing effect of the exhaust gas is further improved.

FIG. 3 shows another embodiment of the device according to the present invention, in which an electric control means is incorporated. The electric control means comprises a vacuum switch 33 to sense the negative pressure at the intake manifold of an automobile engine, a solenoid valve 34 whose solenoid is connected in series with said vacuum switch 33, power source batteries BT connected in series with the series-connected vacuum switch 33 and the solenoid valve 34, and a manual switch 35 connected across the vacuum switch 33. The performance characteristics of the vacuum switch 33 is such that when the automobile is decelerated to reduce the negative pressure at the engine intake manifold, a diaphragm 36 is deflected downwards against the elasticity of a spring 37, as seen in FIG. 3, and accordingly, an actuating rod 38 is pulled downwards to close a contact 39. Thereby a circuit is completed, which traces from one terminal of the batteries BT, through the thus closed contact 39 of the vacuum switch 33 and a solenoid 40 of the solenoid valve 34, and back to the opposite end of the batteries BT.

As a result of it, a current flows through the solenoid 40, to pull an armature 41 rightwards against the elasticity .of a spring 42, as seen in FIG. 3. Thus, the solenoid valve 34 is opened and the space A above a piston 21 is communicated with the branch 7 through the thus opened solenoid valve 34, so that a butterfly valve (FIGS. 1 and 2) can be closed in the same manner as described in detail in the foregoing, referring surface of the armature 41, so as to establish airtight contact between the end of pipe 13 and the armature 41 for interrupting the communication through the solenoid valve 34 when it is deenergized.

In the last-mentioned embodiment, the operation of the solenoid valve 34 is controlled by the vacuum switch 33, but the actuator of the solenoid valve in the device of the invention is not limited to only such vacuum switch. For instance, an accelerator switch, a clutch switch, and a gear neutral switch can be connected in series, so that the solenoid valve can be actuated only when i.e. accelerator is not stepped down while connecting the clutch with the gear at any position other than neutral position.

In the preceding embodiment, a vacuum switch 33 is used to actuate a solenoid valve 34, but the present invention is not limited to the use of such vacuum switch, and any other means capable of detecting the coasting condition of automobiles can be also used for actuating the solenoid valve 34. FIG. 4 shows another embodiment of the present invention, using three electric switches, i.e. a clutch switch 46, an accelerator switch 47, and a gear neutral switch48, for the purpose of detecting the coasting operation of an automobile. FIG. 5 shows an electric switch 'usable in the embodiment of FIG. 4, which comprises brushes 49, 52, a push rod 51 made of electric insulating material, an electric conductor member 50 secured to the push rod 51, a bias spring 54, and terminals B and C. When the push rod 51 is raised against the elasticity of the spring 54, as shown by solid lines in FIG. 5, a circuit between the terminals B and C is completed through the electric conductor member 50. On the other hand, when the rod 51 is lowered by the spring 54, the circuit between the terminals B and C is interrupted.

Referring to FIG. 5, during coasting of an automobile, neither a clutch pedal nor an accelerator pedal is stepped down, and the push rods 51 of the clutch switch 46 and the accelerator switch 47 are so arranged that the push rods SI are raised by the engagement between the lower end 53 of the rod and such pedal unless the clutch pedal and the accelerator pedal are stepped down. During coasting, the transmission gear occupies an operative position other than its neutral, and the relation of the neutral gear switch 48 to the transmission gear is such that the push rod 51 of the gear neutral switch 48 is lowered only when the transmission gear is at the neutral position, so that the circuit through the gear neutral switch 48 is closed during coasting. Thus, all three switches 46, 47, and 48 are closed during coasting. Therefore, by connecting those three switches in series, the coasting operation of the engine can be detected, and the solenoid valve can be actuated through such switches. More particularly, in FIG. 4, when an automobile runs in coasting mode, a circuit is completed, which traces from one terminal of the power source BT through switches 46, 47, 48, and the solenoid valve 34, and back to the opposite terminal of the power source BT. Upon the actuation, the solenoid 40 acts to pull an armature 41 rightwards against the elasticity of a spring 42 to communicate a pipe 13 to the space A above a piston 21, in the same manner as the preceding embodiment described hereinbefore referring to FIG. 3. At the same time, the right-hand end 44 'of the armature 41 blocks an opening 45 communicating the inside of the solenoid valve to the outside atmosphere.

When the current through the solenoid valve is interrupted, the armature 41 is pushed back leftwards by thespring 42, so as to interrupt delivery of the engine manifold negative pressure to the space A above the piston 21. Thus, the space A communicates with the atmosphere and the piston 21 moves downwards, as seen in FIG. 4.

The manual switch 35 in the circuit of FIG. 3 or FIG. 4 can be closed to improve the fuel consumption in a multicylinder engine during low speed running by actuating only a part of the multicylinders. More particularly, with the switch 35 thus closed, the supply gas mixture delivered to nonvalved cylinders burns well, while those valved cylinders do not receive any supply gas mixture at all, and hence, the overall fuel combustion rate is improved. Thus, the fuel consumption can be improved.

ln HO. 1, if it is assumed that the firing sequence of the four cylinders are in the order of the first, third, fourth, and second, as counted from the uppermost cylinder, then it is preferable to interrupt the intake of supply gas mixture to those cylinders which are not fired in succession, i.e. second and third, when the negative pressure at the intake manifold is high. Thereby, the intervals between explosions become uniform. In other words, the first and the fourth cylinders explode with uniform intervals, and the engine can be balanced. Similarly, in the case of a six-cylinder engine with a firing sequence of first, fifth, third, sixth, second, and fourth cylinders, a perfect balance of engine can be maintained by interrupting the intake of the supply gas mixture to the fourth, fifth, and sixth cylinders.

However, the extent of the interrupting of the intake of the supply gas mixture is not limited to one half of all the cylinders of an engine. if the balance does not present any serious problems to a particular engine, any number of cylinders of the engine may be clocked against the supply of the mixture during deceleration and coasting.

As described in the foregoing, according to the present invention, the fuel supply mechanism to a multicylinder engine is so constructed that during deceleration, the intake of the supply gas mixture is interrupted to some of the engine cylinders, so that the amount of the supply gas mixture delivered to each of the remaining cylinders is increased as compared with the corresponding amount for the case of delivering the mixture to all the cylinders. As a result of it, the compression pressure is increased accordingly, for instance when the mixture supply to two cylinders of a four-cylinder engine is interrupted, the compression pressure in the remaining cylinders is roughly doubled. Thus, the compression pressure exceeds the combustion limit pressure, and accordingly, perfect explosion takes place in the cylinders which is receiving the supply gas mixture. Therefore, the amount of raw hydrocarbons exhausted without burning can be greatly reduced, as compared with the corresponding amount of known engines.

Furthermore, similar interruption of the intake of the supply gas mixture to selected cylinders can be applied during slow driving or coasting, so that the heat efficiency in the cylinders provided with the mixture is improved, and the fuel cost is re- 'markably improved. Moreover, by the proper use of the manual switch 35, the fuel cost can be further improved.

We claim:

1. A device for saving fuel and cleansing the exhaust gas in a multicylinder automobile engine having at least one intake manifold and a carburetor means communicating therewith, and a plurality of branch passages communicating said intake manifold with the engine cylinder inlets, said apparatus comprising, a plurality of butterfly valves mounted in selected branch passages for isolating the engine cylinders connected thereto from said intake manifold, a first spring means biasing said butterfly valves to an open position, a first piston and cylinder assembly for closing said butterfly valves, connecting means connecting said butterfly valves with said first piston, a conduit means having one end thereof communicating with said intake manifold between said carburetor means and said butterfly valves and the other end thereof in communication with said first piston and cylinder assembly on that side of said first piston opposite said connecting means to communicate negative pressure from said intake manifold to said first piston to close said butterfly valve, the second piston and cylinder assembly connected in said conduit means, said second cylinder having a port therein communicating with the ambient atmosphere, said second piston having a first position for communicating said conduit with said first cylinder and a second position for blocking said conduit and connecting said port with said first cylinder, and a second spring means for biasing said second piston to-said second position, and sensing means responding to a coasting condition of the vehicle for moving said second piston to said first position, whereby, when the vehicle is coasting and the intake manifold vacuum is sufficient to overcome the biasing force of said second spring means, said conduit is communicated with said first piston and cylinder assembly to actuate said first piston and positively close said butterfly valves to prevent the selected engine cylinders from receiving a fuel mixture supply.

2. A device for saving fuel and cleansing the exhaust gases of a multicylinder engine as claimed in claim 1 further comprising, an opening in said selected branches of said intake manifold for communicating said selected cylinders with the ambient atmosphere, said opening positioned in said selected branches between the butterfly valves and the engine cylinder inlets, and a valve means having a first position for blocking said openings and a second position for allowing the ambient air to enter said openings, said valve means normally biased to said first position and being controlled by said connecting means to open said opening when said first piston is actuated.

3. Apparatus claimed in claim 1 wherein one end surface of said second piston is communicated with said conduit and the other end surface of said second piston being open to communicate with atmospheric pressure, whereby said second piston is urged to said first position by the pressure difference at both end surfaces prevailing at a coasting condition of the vehicle.

4. Apparatus for saving fuel and cleansing exhaust gas in a multicylinder vehicle engine having at least one intake manifold with a carburetor means and a plurality of branches communicating engine cylinder inlets with the manifold, said apparatus comprising,

a. a plurality of valves mounted in selected branches and operable to isolate selected engine cylinders from said manifold, first spring means biasing said valves to an open position, a first piston and cylinder assembly, connecting means connected between said valves and said first piston for operating said valves, said first cylinder slidably accommodating said first piston, and conduit means connected between said manifold and said first cylinder to communicate negative pressure to one end surface of said first piston means to close said valves,

b. a second cylinder communicating with said conduit means and having a port communicating with said first cylinder, a second piston slidably accommodated in said second cylinder and adapted to establish communication between said first cylinder and said conduit in one position and to interrupt said communication in a second position, and second spring means biasing said second piston to said second position,

c. a solenoid valve means connected to said second cylinder means and operably connected to said second piston to urge said second piston to said one position when said solenoid valve is actuated,

. sensing means responding to a coasting condition of the vehicle for actuating said solenoid valve, whereby said selected engine cylinders receive decreased fuel mixture supply to improve combustion when the vehicle is coastmg.

5. Apparatus as claimed in claim 4 wherein said sensing means comprises a negative manifold pressure sensing means including a vacuum switch connected to said solenoid valve and operably connected to said intake manifold for energizing said solenoid valve when said vehicle is coasting.

6. Apparatus as claimed in claim 4, wherein said sensing means comprises, a clutch pedal actuated switch, said switch being closed when a clutch pedal of said vehicle is in the clutch-engaging position, an accelerator actuated switch, said switch being closed when an accelerator pedal of said vehicle is in the engine idle position, and a transmission gearshift neutral switch, said neutral switch being closed when a transmission of said vehicle is in a driving gear position, said clutch pedal switch, said accelerator pedal switch and said transmission gear switch being connected in series with said solenoid valve to actuate said solenoid when said switches are closed simultaneously. l

7. Apparatus as claimed in claim 6 further comprising, a manual switch shunting said clutch switch, accelerator switch and gear neutral switch.- 

1. A device for saving fuel and cleansing the exhaust gas in a multicylinder automobile engine having at least one intake manifold and a carburetor means communicating therewith, and a plurality of branch passages communicating said intake manifold with the engine cylinder inlets, said apparatus comprising, a plurality of butterfly valves mounted in selected branch passages for isolating the engine cylinders connected thereto from said intake manifold, a first spring means biasing said butterfly valves to an open position, a first piston and cylinder assembly for closing said butterfly valves, connecting means connecting said butterfly valves with said first piston, a conduit means having one end thereof communicating with said intake manifold between said carburetor means and said butterfly valves and the other end thereof in communication with said first piston and cylinder assembly on that side of said first piston opposite said connecting means to communicate negative pressure from said intake manifold to said first piston to close said butterfly valve, the second piston and cylinder assembly connected in said conduit means, said second cylinder having a port therein communicating with the ambient atmosphere, said second piston having a first position for communicating said conduit with said first cylinder and a second position for blocking said conduit and connecting said port with said first cylinder, and a second spring means for biasing said second piston to said second position, and sensing means responding to a coasting condition of the vehicle for moving said second piston to said first position, whereby, when the vehicle is coasting and the intake manifold vacuum is sufficient to overcome the biasing force of said second spring means, said conduit is communicated with said first piston and cylinder assembly to actuate said first piston and positively close said butterfly valves to prevent the selected engine cylinders from receiving a fuel mixture supply.
 2. A device for saving fuel and cleansing the exhaust gases of a multicylinder engine as claimed in claim 1 further comprising, an opening in said selected branches of said intake manifold for communicating said selected cylinders with the ambient atmosphere, said opening positioned in said selected branches between the butterfly valves and the engine cylinder inlets, and a valve means having a first position for blocking said openings and a second position for allowing the ambient air to enter said openings, said valve means normally biased to said first position and being controlled by said connecting means to open said opening when said first piston is actuated.
 3. Apparatus claimed in claim 1 wherein one end surface of said second piston is communicated with said conduit and the other end surface of said second piston being open to cOmmunicate with atmospheric pressure, whereby said second piston is urged to said first position by the pressure difference at both end surfaces prevailing at a coasting condition of the vehicle.
 4. Apparatus for saving fuel and cleansing exhaust gas in a multicylinder vehicle engine having at least one intake manifold with a carburetor means and a plurality of branches communicating engine cylinder inlets with the manifold, said apparatus comprising, a. a plurality of valves mounted in selected branches and operable to isolate selected engine cylinders from said manifold, first spring means biasing said valves to an open position, a first piston and cylinder assembly, connecting means connected between said valves and said first piston for operating said valves, said first cylinder slidably accommodating said first piston, and conduit means connected between said manifold and said first cylinder to communicate negative pressure to one end surface of said first piston means to close said valves, b. a second cylinder communicating with said conduit means and having a port communicating with said first cylinder, a second piston slidably accommodated in said second cylinder and adapted to establish communication between said first cylinder and said conduit in one position and to interrupt said communication in a second position, and second spring means biasing said second piston to said second position, c. a solenoid valve means connected to said second cylinder means and operably connected to said second piston to urge said second piston to said one position when said solenoid valve is actuated, d. sensing means responding to a coasting condition of the vehicle for actuating said solenoid valve, whereby said selected engine cylinders receive decreased fuel mixture supply to improve combustion when the vehicle is coasting.
 5. Apparatus as claimed in claim 4 wherein said sensing means comprises a negative manifold pressure sensing means including a vacuum switch connected to said solenoid valve and operably connected to said intake manifold for energizing said solenoid valve when said vehicle is coasting.
 6. Apparatus as claimed in claim 4, wherein said sensing means comprises, a clutch pedal actuated switch, said switch being closed when a clutch pedal of said vehicle is in the clutch-engaging position, an accelerator actuated switch, said switch being closed when an accelerator pedal of said vehicle is in the engine idle position, and a transmission gearshift neutral switch, said neutral switch being closed when a transmission of said vehicle is in a driving gear position, said clutch pedal switch, said accelerator pedal switch and said transmission gear switch being connected in series with said solenoid valve to actuate said solenoid when said switches are closed simultaneously.
 7. Apparatus as claimed in claim 6 further comprising, a manual switch shunting said clutch switch, accelerator switch and gear neutral switch. 